The effect of COVID-19 lockdown on particulate matters concentration: Case of land use regression difference modeling in Bangkok, Thailand

COVID-19 lockdowns around the world led to significant reductions in anthropogenic emissions, especially in developing countries across Asia. Our study, conducted in Bangkok, Thailand presents a more granular picture; while the annual average fine particulate matter (PM_2.5) decreased by 23.8% during lockdowns, these pandemic restrictions had relatively less impact on particulate matter (PM₁₀) and coarse particles (PM_c). To provide a more comprehensive understanding of the effects of lockdown measures on particulate matter concentrations, this study employed a Land Use Regression (LUR) model. This research confirmed that a reduction in anthropogenic emissions, particularly in commercial and institutional areas could potentially reduce the PM_2.5 concentration. Our results indicated that residential land use in Bangkok was not associated with higher PM_2.5 levels than before the COVID-19 pandemic although Bangkok residents spent more time at home during lockdowns. In addition, Buddhist temple activities did not have a significant impact on PM_2.5 levels. Although deaths due to COVID-19 and air pollutants from furnace cremations increased, the impact of cremations on PM_2.5 was offset by a decrease in normal temple activities, such as burning incense. These evolving changes in anthropogenic emissions specific to different land uses deserve special attention from policymakers, especially as the Thai economy resumes full operations post-pandemic.